In the past, a commodity sales data processing apparatus such as a POS (Point Of Sales) terminal is used for checkout processing in commodity sales stores such as a supermarket and a convenience store. The commodity sales data processing apparatus includes an operator side display that displays processing content to an operator, a customer side display that displays checkout information and the like to a customer, a scanner that reads barcodes attached to commodities, a keyboard that receives the input of characters and the like by the depression of operation keys, and a card reader that reads information stored in a magnetic card such as a credit card.
The operator side display is designed to have a wide angle of field to allow an operator to visually recognize displayed content even if an angle for viewing a screen changes because of the difference in height of operators, the slight difference in posture during work, or the like. It is a general practice to also set, taking into account display performed to aim at the effectiveness of advertising such as commercial videos, the customer side display to have a wide angle of field to allow the customer to visually recognize displayed content from various angles.
In recent years, a self-type commodity sales data processing apparatus is spreading. In checkout processing employing the self-type commodity sales data processing apparatus, a customer, rather than an operator, carries out a series of operation. Therefore, for a store, there is an advantage that personnel expenses for operators can be reduced. Further, for customers, there is an advantage that privacy is protected because purchased commodities are not known by the operators.
When the settlement of a transaction is performed by using a credit card or a debit card or when a point, card is used, personal information such as a credit card number, age, sex, a name, the number of points of a customer could be displayed on the operator side display. Therefore, from the viewpoint of protection of the personal information, some store takes measures of bonding a film having a very small louver layer to the surface of the operator side display to narrow the angle of field.
As a technique for protecting the personal information displayed on the screen in the same manner, a display apparatus disclosed in JP-A-2006-259930 is known. This display apparatus includes peep preventing means, an image photographing device, and counting means for detecting faces images with the image photographing device and counting the number of detected face images. When plural face images are counted by the counting means, the peep preventing means is caused to operate.
As described in JP-A-2008-107404, a display apparatus is developed that can electrically adjust an angle of field using a transparent-scattering switching element such as PNLC (Polymer Network Liquid Crystal) having polymer dispersion liquid crystal nipped by substrates provided with transparent electrodes.
In the display apparatus disclosed in JP-A-2008-107404, the refractive indexes of a polymer chain and the polymer dispersion liquid crystal are the same in a state in which voltage is applied between the transparent electrode pair. The transparent-scattering switching element changes to a transparent state. In this state, since an emission angle range of light emitted from a light source is limited, an angle of field of a display screen is narrowed. On the other hand, in a state in which voltage is not applied between the transparent electrode pair, the refractive indexes of the polymer chain and the polymer dispersion liquid crystal are different. In this state, the light emitted from the light source scatters when the light passes through the transparent-scattering switching element. Therefore, since the emission angle range of the light emitted from the light source is expanded, the angle of field of the display screen is widened.
On a display included in the self-type commodity sales data processing apparatus, commercial information for advertising commodities and a store, guidance of an operation method, and the like are displayed. Therefore, usually, an angle of field of the display is designed wide in order to improve the visibility of a display screen.
On the display, for example, information concerning commodities registered as purchased commodities is displayed besides the commercial information, the guidance, and the like. Among customers, there are many customers who hate that information concerning purchased commodities are known by others. However, since the angle of field of the display is designed wide as explained above, there is the probability that, especially during busy time of a store, information concerning commodities displayed on the display is known by, for example, other customers waiting in line behind a customer who is operating the commodity sales data processing apparatus.
As explained above, when the film having the very small louver layer is bonded to the display to cope with such a problem, the angle of field is always narrowed and the effectiveness of advertising by the commercial information cannot be obtained. It is always difficult for the customer who is operating the commodity sales data processing apparatus to see an operation screen. Therefore, even when the customer is performing processing that may be peeped, it is difficult to perform operation. In the case of a display with a pressure sensitive touch panel bonded to a display to enable touch operation, input sensitivity of the touch panel falls.
In the technique disclosed in JP-A-2006-259930, the peep preventing means is caused to operate according to only the number of face images shown on the image photographing device irrespectively of content displayed on the display screen. Therefore, the peep preventing means operates even when content that may be seen by anybody such as commercial information is only displayed.